Interbody fusion more cost-effective with better functional outcomes than posterolateral fusion


New research, published by The Spine Journal, has compared the cost-effectiveness of interbody fusions and posterolateral fusion. The study found that when second reoperations were included, interbody fusion results in moderate long-term cost savings and better functional outcomes.

Lead author Mohamad Bydon and colleagues, John Hopkins University School of Medicine, Baltimore, USA, note that “Reimbursements for interbody fusions have declined recently because of their questionable cost-effectiveness.” The authors decided to carry out this study to explore the relative cost-effectiveness and efficacy of the procedure.

The research was formed by decision model analysis based on retrospective data from a single institutional series, enrolling 137 patients who had undergone first-time instrumented lumbar fusions for degenerative or isthmic spondylolisthesis. Quality of life adjustments and expenditures were assigned to each short-term complication (durotomy, surgical site infection, and medical complication) and long-term outcome (bowel/bladder dysfunction and paraplegia, neurologic deficit, and chronic back pain).

Patients were divided into a posterolateral fusion cohort and a posterolateral fusion plus either posterior lumbar interbody fusion (PLIF) or transforaminal interbody fusion (TLIF) cohort. Anterior techniques and multilevel interbody fusions were excluded. Each short-term complication and long-term outcome was assigned a numerical quality-adjusted life-year (QALY), based on time trade-off values in the Beaver Dam Health Outcomes Study. The cost data for short-term complications were calculated from charges accrued by the institution’s finance sector, and the cost data for long-term outcomes were estimated from the literature. The difference in cost of PLF plus PLIF/TLIF from the cost of PLF alone divided by the difference in QALY was defined as the cost-effectiveness ratio in this study.

Of 137 first-time lumbar fusions for spondylolisthesis, 83 patients underwent posterolateral fusion and 54 underwent PLIF/TLIF. The average time to reoperation was 3.5 years. The mean QALY over 3.5 years was 2.81 in the posterolateral fusion cohort versus 2.66 in the PLIF/TLIF cohort (p=0.110). The mean 3.5-year costs of US$54,827.05 after index interbody fusion were statistically higher than that of the US$48,822.76 after posterolateral fusion (p= 0.042). The cost-effectiveness ratio of interbody fusion to posterolateral fusion after the first operation was −US$46,699.40 per QALY; however, of the 27 patients requiring reoperation, the reoperation rate ratio was 7.89 times higher after posterolateral fusion (2.91, 26.67). The cost-effectiveness ratio after the first reoperation was −US$24,429.04 per QALY (relative to posterolateral fusion). Two patients in the posterolateral fusion cohort required a second reoperation, whereas none required a second reoperation in the PLIF/TLIF cohort. Taken collectively, the total cost-effectiveness ratio for the interbody fusion is US$9,883.97 per QALY.

Bydon et al report that “The reoperation rate was statistically higher for posterolateral fusion, whereas the negative cost-effectiveness ratio for the initial operation and first reoperation favours posterolateral fusion. However, when second reoperations were included, the cost-effectiveness ratio for the interbody fusion became US$9,883.97 per QALY, suggesting moderate long-term cost savings and better functional outcomes with the interbody fusion.”